How is ceramic tile made?

­Our favorite superheroes come with a wide variety of powers and abilities, all the better to fight off dastardly villains. We study comic books and line up for movies to see how the best superheroes take on evil without breaking a sweat. Sometimes, what makes a hero so compelling is the origin story -- how he or she got to be the hero we depend upon.

Now, it's likely that even the biggest home improvement geek in the world isn't beating down doors with ideas for a cer­amic tile superhero, but that doesn't mean that ceramic tile doesn't come with a whole host of amazing abilities. Ceramic tile makes for a beautiful wall and flooring material, but it's more than just a pretty face. These tiles also boast of durability and natural resistance to enemies including fire, frost, moisture and stains. And ceramic tile has had adventures galore, enough to match if not exceed Batman and Superman. After all, even those superheroes weren't around to decorate king's palaces in ancient Europe or churches in Renaissance Ita­ly. Yet ceramic tile remains a humble hero; even modest homes may glory in ceramic tile's presence in the kitchen or the bathroom.

­So what is this superhero's back story? If Peter Parker was bitten by a radioactive spider and the Green Lantern gets powers from a magical ring, then how is ceramic tile made into the mighty force that it is today? It's really quite simple -- a ceramic tile is just clay that's formed, glazed and baked. And remarkably, for ceramic tile's long, illustrious history, very little has changed. The same ingredients are still used, and the process is still basically the same, though it has been updated and mechanized to allow for faster production.

Ceramic tiles were once made by hand. Wet clay was fashioned into shape, sometimes with the help of a wooden mold, and then left to dry in the sun or fired in a small brick kiln. While a few artisans still craft ceramic tiles by hand, the majority of ceramic tiles made today go through a process known as dry pressing or dust pressing. This process requires much less labor and time, which is part of the reason that ceramic tile is not just for Egyptian kings anymore. Go to the next page to find out the steps of making ceramic tile, a process that involves our main character taking on several different pseudonyms. There may be more steps than the single bound that Superman needs to leap tall buildings, but it's impressive all the same.

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Making Ceramic Tiles

From the side of a tile, you can see where the glaze meets the bisque.

Ceramic tile starts life as a lump of earth -- everything in that final product is a natural material. Ea­ch manufacturer likely has its own time-tested recipe for ceramic tile, but clay is usually the main ingredient, along with other items such as sand, feldspar, quartz and water. These ingredients are mixed and grounded up in a ball mill to create what's known as the body slip. Body slip is used to differentiate the body of the tile from its glazed topping; it's the chocolate cake to vanilla frosting. At this point, the body slip contains about 30 percent water [source: American Tile]. That moisture helps adhere the ingredients to each other, but as soon as its job is done, it's out of there. To accomplish this, the body slip is put into a dryer and heated; the moisture content is reduced to about 6 percent [source: American Tile].

After that time in the dryer, the body slip is now essentially powder, or dust. As you may remember from the last page, this entire process is sometimes called dust pressing -- and you're about to learn why. The dust is placed into a large press, powered either with electricity or hydraulics. The press pushes the dust into a set size and shape with a force ranging from a few hundred pounds a square inch to 100,000 pounds per square inch (689,475.7 Newtons per square meter) [source: Bedrosians]. That pressure is what gives the finished project its tensile strength. While we commonly see square or rectangular ceramic tile, presses may have shaped imprints to create ovals, diamonds and other unique shapes as well. The shaped body is called the bisque. After the body is formed, it's dried out to remove all last traces of moisture.

­Now it's time for that frosting we mentioned -- the glaze. The word comes from the Old English word for glass, which is a good description of glaze. It's that glassy looking substance on one side of the tile. Just as there's a wide variety of delicious frostings, there are many choices for the glaze, including matte and high-gloss, and many ways of applying glaze, from spray to silkscreen. To give the tile some color, pigments are mixed in with the other ingredients. However, even if very vibrant pigments are used, the piece will still look fairly pale, and not like the vibrant tiles we see in the store. That process won't happen until the next step. Though glazing is a typical step for ceramic tile, it's not essential. Not every tile has to be glazed to be considered ceramic.­

But there is one qualification that ceramic tiles do have to meet -- they all have to be baked. Before it goes in the kiln, the product has acquired another name: green tile. Find out how the final transformation to ceramic tile occurs on the next page.

What's the Difference between Porcelain and Ceramic Tile?­

Have you settled on ceramic tile for the bathroom, only to be told you should consider porcelain tiles? Porcelain tiles actually are ceramic tiles; porcelain is one type of ceramic clay. To be considered porcelain, the tile must meet certain water absorption rates, though; the tile can't absorb more than 0.5 percent of its weight in water [source: Bridge]. Tiles that meet this rating are considered "impervious."

Firing Ceramic Tiles

Dazzle your buddies at the soda fountain by explaining how these tiles were made.

After the glaze has been applied, it's time to put the tiles in the kiln to be fired. Traditionally, ceramic tile was left to bake for several hours in what's known as a periodic kiln, such as a beehive kiln. It was the continuous kiln, however, that made the production process of ceramic tile more efficient in the last century. Continuous kilns include tunnel kilns and roller-hearth kilns.

­If you've ever been to a sandwich shop where the worker heats the sandwich by giving it a ride through the toaster, then you'll understand these new types of kilns. Rather than sitting in the heat for hours, the ti­le is rolled through by conveyor belt-type contraptions (the specific apparatus varies from kiln to kiln). The heat inside the kiln is precisely monitored and controlled by computer. In the first half of the tile's journey, things are starting to get warm.

At the center point, maximum temperature, which can be as high as 2,500 degrees Fahrenheit (1,371.1 degrees Celsius), is reached [source: Donegan]. The higher the temperature, the stronger the brick. As the tile makes its way to the opposite side of the tube, it's gradually cooling down. The cooling down period isn't as passive as it might sound, though -- tiles are still changing color. With these rolling, or continuous kilns, the process has gone from hours of stationary baking to less than an hour. That allows the manufacturers to make a lot more tile, at a reasonable price for the marketplace.

The process was also expedited by the resurgence of the monocottura method. Monocottura, an Italian term meaning "fired once," gives ceramic tile a lot more strength. This additional strength is what allowed tile to go from a product best suited for walls to one that is also good for floors [source: Giovannini]. After just one trip through a hot kiln, the tile made with the monocottura method is ready to be sorted and sent off to the store.

If firing a tile just once makes it so much stronger, why bother with any more firings? If you want a tile with many colors or an elaborate pattern, then that tile will be baked with a bicottura method. Though the prefix would indicate that the tile is fired twice, it can actually be fired as many times as necessary. Before each firing, a different colored glaze is applied to the tile, and the process is repeated until the design is complete.

At this point, our superheroic ceramic tile has gone from clay to dust to tile. Ceramic tile may require many more costume changes than Wonder Woman, but it can also go a lot more places in your home than she can.

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